Roll-up closures utilizing a flexible cover or curtain to cover a portal or opening such as a door or window are known. For example, in U.S. Pat. No. 5,566,736, Crider et al. teach a sealable curtain wherein each lateral margin of the cover has a strip of hook and loop fastener material affixed thereto, and a complementary strip is affixed to the lateral margins of the structure defining the portal. A first end of the cover is rigidly affixed across a first margin of the portal. The opposite end of the cover can be upturned and connected to a driven take-up roller mounted next to the first margin of the portal. In this embodiment, an elongated transverse rod is supported within the upturned end of the cover. In a second embodiment, a secondary transverse rod can be utilized to maintain tension on the cover (see FIGS. 1-2 of the U.S. Pat. No. 5,566,736). In a third embodiment, a second curtain can be employed (see FIG. 5 of the U.S. Pat. No. 5,566,736). In any of the embodiments, activation of the driven roller lengthens or shortens the effective length of the cover(s) while positioning the mating hook and loop fasteners to seal and unseal the cover(s) to the lateral margins of the portal.
Although the foregoing portal coverings are very effective in preventing the passage of wind, rain, light, insects, or any other elements through the portal, the use of hook and loop fasteners may not provide air tight seals for controlled environments (e.g. heated rooms, refrigerated rooms, “clean” rooms, or “quiet” rooms) or meet particular industry standards, such as those of the National Sanitation Foundation. For example, hook and loop fasteners tend to retain moisture, which can promote microbial growth, and are noisy while unsealing. Because of these features, hook and loop fasteners may be unacceptable in the case of industrial refrigerators and freezers used for food storage or facilities where low noise is required.
What is needed is a portal covering that can quietly and tightly seal a portal in a controlled environment to prevent the movement of air, moisture, and heat through the portal.